1. Field of the Invention
The present invention relates generally to cable assemblies having semi-hardened network access points that are deployed in fiber optic communications networks. More specifically, the present invention relates to cable assemblies having semi-hardened network access points that are used for routing, securing, and protecting pre-terminated and/or pre-connectorized optical fibers, including fiber optic drop cables and/or tethers, that are branched or withdrawn from a fiber optic distribution cable at mid-span access locations. These network access points are also referred to as “Flexible Network Access Points” (FNAPs or FlexNAP).
2. Technical Background of the Invention
Optical fibers are increasing being used in a variety of broadband applications, including voice, video, and data transmission applications. As a result of this ever-increasing demand, fiber optic communications networks typically include a relatively large number of mid-span access locations at which one or more optical fibers, including drop cables and/or tethers, are branched or withdrawn from a distribution cable. These mid-span access locations provide multiple dedicated optical fiber drops that are used to connect a plurality of subscribers to the networks. Thus, the mid-span access locations are used to extend “all optical” networks to commercial and residential subscribers. In this regard, networks are being developed that deliver “fiber-to-the-curb” (FTTC), “fiber-to-the-business” (FTTB), “fiber-to-the-home” (FTTH), and “fiber-to-the-premises” (FTTP), collectively referred to as “FTTx.” Based upon the increase in the number of mid-span access locations and the unique physical attributes of optical fibers themselves, structure is needed for routing, securing, and protecting the optical fibers at the mid-span access locations during and subsequent to the installation of a distribution cable. Preferably, the structure provides selective access for pre-terminated and/or pre-connectorized optical fibers, including drop cables and/or tethers, while simultaneously protecting the mid-span access locations from exposure to adverse environmental conditions. The structure should not, however, prevent the distribution cable from being deployed through relatively small diameter conduits (e.g., 1.25-inch conduits), or over conventional sheave wheels, rollers, and/or pulleys.
In one exemplary fiber optic communications network, one or more drop cables are interconnected with a distribution cable at a mid-span access location within an aerial splice closure that is suspended from an aerial strand or the distribution cable itself. Substantial expertise and experience are required to configure the optical connections within the closure in the field. In particular, it is often difficult to enter the closure and identify an optical fiber of the distribution cable that is to be interconnected with an optical fiber of the drop cable. Once identified, the optical fiber of the drop cable is typically joined directly to the optical fiber of the distribution cable using a conventional splicing technique, such as fusion splicing. In other instances, the optical fiber of the drop cable and the optical fiber of the distribution cable are first spliced to a relatively short length of optical fiber having a pre-mounted connector on the other end, referred to in the art as a “pigtail.” These pigtails are routed to opposite sides of an adapter sleeve that is disposed within the closure to interconnect the drop cable with the distribution cable. In either case, the process of entering and configuring the closure is not only time consuming, but must be accomplished by a highly-skilled field technician at significant cost and under working conditions that are often less than ideal. Reconfiguring optical fiber connections in an aerial splice closure is especially difficult, particularly in instances in which at least some of the optical fibers of the distribution cable extend uninterrupted through the closure, as the closure cannot be readily removed from the distribution cable.
Other low-volume FlexNAP solutions have included the use of a “bare” MT ferrules disposed within a low-profile molded protective envelope and the use of a “hardened” connector in either an “integrated” configuration or a tethered plug arrangement. These solutions, however, have proven to be too delicate and to have too large of a form factor. In order to reduce costs by permitting less-skilled and less-experienced field technicians to mid-span optical fiber configurations and reconfigurations, communications service providers are increasingly pre-engineering networks and demanding factory-prepared interconnection solutions, referred to as “plug-and-play” type systems.
In response to these demands, fiber optic hardware and equipment manufacturers have developed several approaches to overcome the disadvantages of accessing and splicing optical fibers in the field. In one such approach, drop cables are spliced to a distribution cable in the factory during manufacturing. While advantageous for manufacturing high-quality mid-span access locations in an environmentally-controlled manner, disadvantages include the relatively large size (i.e. diameter) and inflexibility of the distribution cable assembly at the mid-span access locations, as well as the incremental cost associated with dormant drop cables. More importantly, pre-engineered drop cables may not always be able to mitigate misplacement of the mid-span access locations due to inaccurate measurements or installation errors because the drop cables are manufactured with predetermined lengths. As such, these approaches do not completely address the communications service providers' need to reduce installation and deployment costs.
Thus, communications service providers continue to demand low-profile plug-and-play type systems that may be installed and deployed using existing equipment and methods, and that require a minimum amount of field labor for performing interconnections. It would be desirable to provide a robust closure for routing, securing, and protecting pre-terminated and/or pre-connectorized optical fibers, including drop cables and/or tethers, that are branched or withdrawn from a distribution cable at mid-span access locations. It would also be desirable to provide a robust closure for FTTx networks that may be readily reconfigured after installation, such that drop cables may quickly and easily be interconnected at the mid-span access locations. It would further be desirable to factory assemble the closures on the distribution cable at the mid-span access locations with the lowest possible profiles (i.e. outer diameters), while maintaining access to the optical fibers branched or withdrawn from the distribution cable.